JP5793694B2 - Receiver - Google Patents

Description

  The present invention relates to communication technology, and more particularly, to a receiving apparatus that receives a signal including predetermined information.

  Road-to-vehicle communication is being studied to prevent collisions at intersections. In the road-to-vehicle communication, information on the situation of the intersection is communicated between the roadside device and the vehicle-mounted device. Road-to-vehicle communication requires the installation of roadside equipment, which increases labor and cost. On the other hand, if it is the form which communicates information between vehicle-to-vehicle communication, ie, onboard equipment, installation of a roadside machine will become unnecessary. In that case, for example, the current position information is detected in real time by GPS (Global Positioning System), etc., and the position information is exchanged between the vehicle-mounted devices so that the own vehicle and the other vehicle enter the intersection respectively. (See, for example, Patent Document 1).

JP 2005-202913 A

  In a wireless LAN (Local Area Network) compliant with a standard such as IEEE 802.11, an access control function called CSMA / CA (Carrier Sense Multiple Access Collision Aviation) is used. Therefore, in the wireless LAN, the same wireless channel is shared by a plurality of terminal devices. In such CSMA / CA, a packet signal is transmitted after confirming that no other packet signal is transmitted by carrier sense.

  On the other hand, when a wireless LAN is applied to road-to-vehicle communication such as ITS (Intelligent Transport Systems) and vehicle-to-vehicle communication, it is necessary to transmit information to an unspecified number of terminal devices. It is desirable. At this time, if the data to be transmitted by broadcast becomes large, it becomes necessary to divide the data in order to store it in the packet signal. When the transmission data is encrypted, the encryption process is usually performed before being stored in the packet signal. Therefore, when data is divided, it is effective to encrypt the data before the division and to divide the data after the encryption in order to simplify the processing.

  In a communication system using both road-to-vehicle communication and vehicle-to-vehicle communication, the period of road-to-vehicle communication and the period of vehicle-to-vehicle communication are mixed. The data transmitted from the vehicle-mounted device is often small and rarely divided. On the other hand, the data transmitted from the roadside machine is often large and is often divided. If the data transmitted from the roadside machine is large and cannot be transmitted in one road-to-vehicle communication period, the remaining data will be transmitted in the next road-to-vehicle communication period across the vehicle-to-vehicle communication period. .

  When the data before division is encrypted on the transmission side and the data after encryption is divided, the reception side basically cannot determine whether or not it has been tampered with until all the divided data has been decrypted. . Therefore, on the receiving side, the decoding process is started after all the divided data are prepared. However, when other data is included in the divided data, the time until all the divided data is collected becomes longer and the completion of the decoding process is also delayed.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique for suppressing a delay in the end timing of the decryption process on the receiving side that receives a plurality of divided data divided after encryption. It is in.

  In order to solve the above problems, a receiving apparatus according to an aspect of the present invention includes a receiving unit that receives a plurality of packet signals including divided data obtained by dividing data after encryption processing, and a packet received by the receiving unit. And a decryption unit that executes decryption processing corresponding to the encryption processing before all the divided data is obtained for the divided data included in the signal.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the delay of the completion | finish timing of a decoding process can be suppressed in the receiving side which receives the some division | segmentation data divided | segmented after encryption.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. FIGS. 2A to 2D are diagrams showing a superframe format defined in the communication system. FIGS. 3A to 3B are diagrams illustrating the configuration of subframes. FIGS. 4A to 4F are diagrams illustrating frame formats of each layer defined in the communication system. It is a figure which shows an example of the data structure of a security frame. It is a figure which shows the structure of a base station apparatus. It is a figure which shows the structure of the terminal device mounted in the vehicle. FIGS. 8A to 8B are diagrams for explaining the data input timing to the decoding unit and the decoding timing by the decoding unit. It is a figure which shows the structure of the decoding part which concerns on a comparative example. It is a figure which shows the structure 1 of the decoding part which concerns on an Example. It is a figure which shows the structure 2 of the decoding part which concerns on an Example.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a communication system that performs vehicle-to-vehicle communication between terminal devices mounted on a vehicle, and also executes road-to-vehicle communication from a base station device installed at an intersection or the like to a terminal device. As inter-vehicle communication, the terminal device broadcasts a packet signal that stores information such as the speed and position of the vehicle. In addition, the other terminal device receives the packet signal and recognizes the approach of the vehicle based on the above-described information. Here, the base station apparatus repeatedly defines a frame including a plurality of subframes. The base station apparatus selects any of a plurality of subframes for road-to-vehicle communication, and broadcasts a packet signal in which control information and the like are stored during the period of the head portion of the selected subframe.

  The control information includes information related to a period for the base station apparatus to broadcast the packet signal (hereinafter referred to as “road vehicle transmission period”). The terminal device specifies a road and vehicle transmission period based on the control information, and transmits a packet signal by the CSMA method in a period other than the road and vehicle transmission period (hereinafter referred to as “vehicle transmission period”). Thus, since the road-to-vehicle communication and the vehicle-to-vehicle communication are time-division multiplexed, the collision probability of packet signals between them is reduced. That is, when the terminal device recognizes the content of the control information, interference between road-vehicle communication and vehicle-to-vehicle communication is reduced. Note that a terminal device that cannot receive control information from the base station device, that is, a terminal device that exists outside the area formed by the base station device transmits a packet signal by the CSMA method regardless of the frame configuration.

  The base station apparatus encrypts data to be transmitted, and broadcasts a packet signal storing the encrypted data during the road and vehicle transmission period. The maximum size of data that can be stored in the packet signal is determined. When the size of data to be broadcasted exceeds the maximum value, the base station apparatus broadcasts a plurality of packet signals in the road and vehicle transmission period by dividing the encrypted data into a plurality of pieces.

  When the divided encrypted data cannot be transmitted in one road-vehicle transmission period, it is transmitted in two or more road-vehicle transmission periods across the vehicle-vehicle transmission period. When the terminal device receives the divided encrypted data, the terminal device sequentially decodes the decoded data, buffers the decrypted data, and integrates the plurality of buffered decrypted data to transmit the data transmitted from the base station device. Restore.

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. This corresponds to a case where one intersection is viewed from above. The communication system 100 includes a base station device 10, a first vehicle 12a, a second vehicle 12b, a third vehicle 12c, a fourth vehicle 12d, a fifth vehicle 12e, a sixth vehicle 12f, and a seventh vehicle 12g, collectively referred to as a vehicle 12. , The eighth vehicle 12h, and the network 202. Here, only the first vehicle 12 a is shown, but each vehicle 12 is equipped with a terminal device 14. An area 212 is formed around the base station apparatus 10, and an outside area 214 is formed outside the area 212.

  As shown in the drawing, the road that goes in the horizontal direction of the drawing, that is, the left and right direction, intersects the vertical direction of the drawing, that is, the road that goes in the up and down direction, at the center. Here, the upper side of the drawing corresponds to the direction “north”, the left side corresponds to the direction “west”, the lower side corresponds to the direction “south”, and the right side corresponds to the direction “east”. The intersection of the two roads is an “intersection”. The first vehicle 12a and the second vehicle 12b are traveling from left to right, and the third vehicle 12c and the fourth vehicle 12d are traveling from right to left. Further, the fifth vehicle 12e and the sixth vehicle 12f are traveling from the top to the bottom, and the seventh vehicle 12g and the eighth vehicle 12h are traveling from the bottom to the top.

  In the communication system 100, the base station apparatus 10 is fixedly installed at an intersection. The base station device 10 controls communication between terminal devices. The base station device 10 repeatedly generates a frame including a plurality of subframes based on a signal received from a GPS satellite (not shown) and a frame formed by another base station device 10 (not shown). Here, the road vehicle transmission period can be set at the head of each subframe. The base station apparatus 10 selects a subframe in which the road and vehicle transmission period is not set by another base station apparatus 10 from among a plurality of subframes in the frame. The base station apparatus 10 sets a road and vehicle transmission period at the beginning of the selected subframe.

  The base station apparatus 10 notifies the packet signal in the set road and vehicle transmission period. In the road and vehicle transmission period, a plurality of packet signals may be notified. Since the terminal device 14 is mounted on the vehicle 12 as described above, the terminal device 14 is movable. When the terminal device 14 receives the packet signal from the base station device 10, the terminal device 14 generates a frame based on the control information included in the packet signal, in particular, the information about the timing when the road and vehicle transmission period is set and the information about the frame. To do. As a result, the frame generated in each of the plurality of terminal devices 14 is synchronized with the frame generated in the base station device 10. The terminal device 14 notifies the packet signal during the vehicle transmission period. Although the vehicle transmission period will be described later, it can be said that this is a period different from the road and vehicle transmission period in the frame. Here, CSMA / CA is executed in the vehicle transmission period.

  The terminal device 14 acquires data and stores the data in a packet signal. The data includes, for example, information related to the location. The terminal device 14 also stores control information received from the base station device 10 in the packet signal. That is, the control information transmitted from the base station device 10 is transferred by the terminal device 14. On the other hand, when it is estimated that the terminal apparatus 14 exists outside the area 214, the terminal apparatus 14 notifies the packet signal by executing CSMA / CA regardless of the frame configuration.

  2A to 2D show a superframe format defined in the communication system 100. FIG. FIG. 2A shows the structure of the super frame. The superframe is formed by N subframes indicated as the first subframe to the Nth subframe. For example, when the length of the superframe is 100 msec and N is 8, a subframe having a length of 12.5 msec is defined. N may be other than 8.

  FIG. 2B shows a configuration of a super frame generated by the first base station apparatus 10a. The first base station device 10a corresponds to any one of the base station devices 10. The first base station apparatus 10a sets a road and vehicle transmission period at the beginning of the first subframe. Moreover, the 1st base station apparatus 10a sets a vehicle transmission period following a road and vehicle transmission period in a 1st sub-frame. The vehicle transmission period is a period during which the terminal device 14 can notify the packet signal. That is, in the road and vehicle transmission period which is the head period of the first subframe, the first base station device 10a can notify the packet signal, and in the vehicle and vehicle transmission period subsequent to the road and vehicle transmission period of the first subframe, the terminal device 14 is defined such that a packet signal can be broadcast. Furthermore, the first base station apparatus 10a sets only the vehicle transmission period from the second subframe to the Nth subframe.

  FIG. 2C shows a configuration of a super frame generated by the second base station apparatus 10b. The second base station apparatus 10b corresponds to a base station apparatus 10 different from the first base station apparatus 10a. The second base station apparatus 10b sets a road and vehicle transmission period at the beginning of the second subframe. Also, the second base station apparatus 10b sets the vehicle transmission period from the first stage of the road and vehicle transmission period in the second subframe, from the first subframe and the third subframe to the Nth subframe.

  FIG. 2D shows a configuration of a super frame generated by the third base station apparatus 10c. The third base station apparatus 10c corresponds to a base station apparatus 10 different from the first base station apparatus 10a and the second base station apparatus 10b. The third base station apparatus 10c sets a road and vehicle transmission period at the beginning of the third subframe. In addition, the third base station apparatus 10c sets the vehicle transmission period from the first stage of the road and vehicle transmission period in the third subframe, the first subframe, the second subframe, and the fourth subframe to the Nth subframe. As described above, the plurality of base station apparatuses 10 select different subframes, and set the road and vehicle transmission period at the head portion of the selected subframe.

  FIGS. 3A to 3B show subframe configurations. As shown to Fig.3 (a), a sub-frame is comprised in order of the road vehicle transmission period and the vehicle transmission period. In the road and vehicle transmission period, the base station device 10 can notify the packet signal, and in the vehicle and vehicle transmission period, the terminal device 14 can notify the packet signal. FIG. 3B shows the arrangement of packet signals during the road and vehicle transmission period. As illustrated, a plurality of RSU (Load Side Unit) packet signals are arranged in the road and vehicle transmission period. Here, the front and rear packet signals are separated by SIFS (Short Interframe Space).

  4A to 4F show the frame formats of the respective layers defined in the communication system 100. FIG. FIG. 4A shows the frame format of the physical layer. As shown in the figure, a PLCP preamble, a PLCP header, a PSDU (Physical Layer Service Data Unit), and a tail are sequentially arranged in the frame. The physical layer frame corresponds to the packet signal described above. FIG. 4B shows a frame format of the MAC layer. This frame is stored in the PSDU of FIG. As illustrated, a MAC header, an MSDU (MAC Layer Service Data Unit), and an FCS (Frame Check Sequence) are sequentially arranged in the frame. FIG. 4C shows a frame format of the LLC layer. This frame is stored in the MSDU of FIG. As illustrated, an LLC header and an LSDU (LLC Layer Service Data Unit) are sequentially arranged in the frame.

  FIG. 4D shows the frame format of the inter-vehicle / road-vehicle shared communication control information layer. This frame is stored in the LSDU of FIG. As shown in the figure, an IR header and an APDU (Application Protocol Data Unit) are sequentially arranged in the frame. FIG. 4E shows the frame format of the security layer. This frame is stored in the APDU of FIG. As illustrated, a security header (Security Header), a payload (Payload), and a security footer (Security Footer) are sequentially arranged in the frame. FIG. 4F shows the frame format of the application layer. This frame is stored in the payload of FIG. 4E, and is composed of application data.

  FIG. 5 shows an example of the data structure of the security frame. This is a detailed diagram of the contents of FIG. The security header includes a version (VER), a message type (MT), key information, a nonce, and a data length. The version (VER) indicates the version of the frame format and is a fixed value (= 0). The data length of the version (VER) is 1 byte. A message type (MT) designates a message type, a data authentication method, and the like. The data length of the message type (MT) is 0.5 bytes. The most significant bit (MSB) of the data length is a management application flag and indicates the presence or absence of a management field. “0” indicates no presence and “1” indicates presence. Bit 2 indicates a data authentication method and indicates a data authentication method. “0” indicates a message authentication code (MAC) method, and “1” indicates an electronic signature method. Bit 1 and the least significant bit (LSB) indicate the message format. “0” indicates no authentication data, “1” indicates data with authentication, “2” indicates encrypted data with authentication, and “3” indicates reservation.

  The key information includes a flag, a master key, a communication key, and a key ID. The master key, communication key, and key ID are optional. The flag indicates the presence / absence of a subsequent field in the key information. The data length of the flag is 0.5 bytes. The most significant bit (MSB) is the master key (may be encrypted), bit 2 is the communication key (may be encrypted), bit 1 is the key ID, and the least significant bit (LSB) is reserved (= 0). In each bit, “0” indicates absence and “1” indicates presence. Therefore, when all the bits are “0”, this indicates that the field is omitted. The master key indicates a new master key encrypted with the immediately preceding master key. The data length of the master key is 16 bytes. The communication key indicates a communication key encrypted with the latest master key. The data length of the communication key is 16 bytes. The key ID indicates an identification number for referring to the key table. The data length of the key ID is 1 byte. Nonse includes transmission source information and transmission date and time. The transmission source information indicates the device ID of the transmission source. The data length of the sender information is 4 bytes. The transmission date / time indicates a message transmission date / time or a counter value. The data length of the transmission date / time is 6 bytes. The data length indicates the byte length of the payload. The data length is in the range of 1 to 2 bytes.

  The payload is subject to concealment by the communication key and message authentication. The payload includes a management application and a service application. The management application shows security management application data and is an option. The service application indicates application data. The data length of the management application and service application is variable.

  The security footer includes data authentication. Data authentication indicates a message authentication code (MAC) or electronic signature. The data length for data authentication is 12 bytes for the former and 56 bytes for the latter. In general, a message authentication code (MAC) is encrypted by a common key encryption method, and an electronic signature is encrypted by a public key encryption method. Hereinafter, an example in which a message authentication code (MAC) is used for data authentication will be described in this specification.

  FIG. 6 shows the configuration of the base station apparatus 10. The base station apparatus 10 includes an antenna 20, an RF unit 22, a modem unit 24, a MAC frame processing unit 26, a security processing unit 28, a control unit 30, a network communication unit 32, and a data generation unit 34. The security processing unit 28 includes an encryption unit 36 and a decryption unit 38.

  The RF unit 22 receives a packet signal from the terminal device 14 (not shown) or another base station device 10 by the antenna 20 as a reception process. The RF unit 22 performs frequency conversion on the received radio frequency packet signal to generate a baseband packet signal. Further, the RF unit 22 outputs a baseband packet signal to the modem unit 24. In general, baseband packet signals are formed by in-phase and quadrature components, so two signal lines should be shown, but here only one signal line is shown for clarity. Shall be shown. The RF unit 22 includes an LNA (Low Noise Amplifier), a mixer, an AGC, and an A / D conversion unit.

  As a transmission process, the RF unit 22 performs frequency conversion on the baseband packet signal input from the modem unit 24 to generate a radio frequency packet signal. Further, the RF unit 22 transmits a radio frequency packet signal from the antenna 20 during the road-vehicle transmission period. The RF unit 22 also includes a PA (Power Amplifier), a mixer, and a D / A conversion unit.

  The modem unit 24 demodulates the baseband packet signal from the RF unit 22 as a reception process. Further, the modem unit 24 outputs the demodulated result to the MAC frame processing unit 26. Further, the modem unit 24 performs modulation on the MAC frame from the MAC frame processing unit 26 as transmission processing. Further, the modem unit 24 outputs the modulated result to the RF unit 22 as a baseband packet signal. Here, since the communication system 100 corresponds to an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, the modem unit 24 also performs FFT (Fast Fourier Transform) as reception processing and IFFT (Inverse Fast Forward) as transmission processing. Also execute.

  The MAC frame processing unit 26 extracts a security frame from the MAC frame from the modem unit 24 and outputs it to the security processing unit 28 as a reception process. The MAC frame processing unit 26 adds a MAC header, an LLC header, and an IR information header to the security frame from the security processing unit 28 as a transmission process, generates a MAC frame, and outputs the MAC frame to the modem unit 24. . Further, the packet signal transmission / reception timing is controlled so that packet signals from other base station apparatuses 10 or terminal apparatuses 14 do not collide.

  The network communication unit 32 is connected to the external network 202. The network communication unit 32 receives road information related to construction and traffic jams from the external network 202. Further, the network communication unit 32 outputs the processing result by the security processing unit 28 to the external network 202. The data generation unit 34 generates service application data using information from a sensor, a camera (not shown), or the like. Then, the message format is designated according to the contents of the service application data, and the generated application data and its data length are output to the security processing unit 28. The control unit 30 controls processing of the entire base station apparatus 10.

  The security processing unit 28 generates or interprets a security frame. When receiving the service application data from the data generation unit 34 as the transmission process, the security processing unit 28 generates a security frame to be output to the MAC frame processing unit 26 based on the received service application data. For example, the service application data received from the data generation unit 34 is set in the service application of the payload shown in FIG. 5, and the data length is set to the data length of the security header. Also, the communication key (random number) encrypted with the master key is set in the communication key of the key information in the security header. In addition, a message authentication code (MAC) generated using the communication key (random number) is set in the security footer. Then, a security frame is generated by adding other security headers. Thereafter, when the designated message format is encrypted data with authentication, the payload and the message authentication code (MAC) are encrypted using the communication key (random number).

  The security processing unit 28 receives a security frame from the MAC frame processing unit 26 as a reception process. The security processing unit 28 confirms the contents of the security header in the security frame. If the message format is data with authentication, the decryption unit 38 performs message verification processing. When the message format is encrypted data with authentication, the decryption unit 38 performs message decryption processing and verification processing. If the message format is plain text, these processes are omitted.

  When the message format is data with authentication, the encryption unit 36 generates a message authentication code (MAC) for the payload using a communication key (random number). The message authentication code (MAC) is generated by applying a MAC algorithm using an AES (Advanced Encryption Standard) -CBC (Cipher Block Chaining) mode. Note that Nonce and data length are also used for generating the MAC.

  When the message format is encrypted data with authentication, the encryption unit 36 adds a message authentication code (MAC) to the payload and encrypts the payload and the message authentication code (MAC). For this encryption, an AES-CCM (Counter with CBC-MAC) mode using a communication key (random number) is applied. In addition to the communication key (random number), a nonce and a data length are used for generating a message authentication code (MAC) for the payload and for encrypting the payload and the message authentication code (MAC). This is based on the algorithm of the CBC-MAC and CCM modes. By using the nonce, different message authentication codes (MAC) and ciphertexts can be obtained even if the payload and the communication key are the same. Note that a message authentication code (MAC) may be added after the payload is encrypted without applying the AES-CCM mode.

  Note that the process of interpreting the security frame performed as the reception process by the decoding unit 38 is the same as the reception process of the terminal device 14 described later.

  In this embodiment, it is assumed that authenticated data or encrypted data with authentication is selected as the message format. In this specification, it is assumed that generation of a message authentication code (MAC) or electronic signature is also included in the broad encryption. Hereinafter, an example will be considered in which the data size of the security frame generated by the security processing unit 28 exceeds the size that can be stored in one packet signal.

  The MAC frame processing unit 26 divides the security frame to be notified into a plurality of partial data (hereinafter referred to as divided data), and then includes the divided data in the packet signal, so that a plurality of information to be notified in the road and vehicle transmission period. Packet signal is generated. Here, the MAC frame processing unit 26 generates divided data by dividing the data for each maximum value of data that can be stored in the packet signal. This process is repeated until data having a size smaller than the maximum value remains, and the MAC frame processing unit 26 sets the remaining data as the last divided data.

  When the data size of the security frame to be notified exceeds the size that can be transmitted in one road-vehicle transmission period, the MAC frame processing unit 26 is the next and subsequent roads in which the base station device 10 can store data. The divided data that could not be stored in the packet signal arranged in the current road-vehicle transmission period is stored in the packet signal arranged in the vehicle transmission period. For example, the maximum value of data that can be stored in one packet signal is set to 1.5 kB, and the maximum size that can be transmitted in one road and vehicle transmission period is set to 4 kB.

  FIG. 7 shows a configuration of the terminal device 14 mounted on the vehicle 12. The terminal device 14 includes an antenna 50, an RF unit 52, a modem unit 54, a MAC frame processing unit 56, a security processing unit 58, a control unit 60, a reception processing unit 62, a notification unit 64, and a data generation unit 66. The security processing unit 58 includes an encryption unit 68 and a decryption unit 70. The antenna 50, the RF unit 52, the modem unit 54, and the MAC frame processing unit 56 execute the same processing as the antenna 20, the RF unit 22, the modem unit 24, and the MAC frame processing unit 26 in FIG. Here, the difference will be mainly described.

  The reception processing unit 62 is based on the data received from the security processing unit 58 and the vehicle information of the own vehicle received from the data generation unit 66, and the risk of collision, the approach of an emergency vehicle such as an ambulance or fire engine, and the road in the traveling direction. And estimation of traffic congestion at intersections. Further, if the data is image information, the data is displayed on the notification unit 64.

  The notification unit 64 includes means for notifying a user such as a monitor, a lamp, and a speaker (not shown). In accordance with an instruction from the reception processing unit 62, the driver is notified of the approach of another vehicle (not shown) via the notification means. In addition, traffic information, image information such as intersections, and the like are displayed on the monitor.

  The data generation unit 66 specifies a current position, a traveling direction, a moving speed, and the like of the vehicle 12 on which the terminal device 14 is mounted based on information supplied from a GPS receiver, a gyroscope, a vehicle speed sensor, and the like (not shown). The current position is indicated by latitude / longitude. Since the method for identifying these pieces of information can be realized by a generally known technique, description thereof is omitted here. The data generation unit 66 generates data to be notified to other terminal devices 14 and the base station device 10 (not shown) based on the specified information, and sends the generated data (hereinafter referred to as application data) to the security processing unit 58. Output. Then, the message format is designated according to the contents of the application data, and the generated application data and its data length are output to the security processing unit 58. Further, the specified information is output to the reception processing unit 62 as vehicle information of the own vehicle. The control unit 60 controls processing of the entire terminal device 14.

  The security processing unit 58 generates or interprets a security frame as a transmission process. The security processing unit 58 generates a security frame to be output to the MAC frame processing unit 56. For example, application data is set in the service application of the payload shown in FIG. Further, the key ID of the communication key used for generating the message authentication code (MAC) is set in the key ID of the key information in the security header, and the own device ID and time are set in Nonce. Also, a message authentication code (MAC) generated using the communication key specified by the key ID is set in the security footer. Then, a security frame is generated by adding other security headers. When the message format is encrypted data with authentication, the message is concealed by encrypting the payload and the message authentication code (MAC) using the communication key. If the message format is plain text, these processes are omitted.

  The security processing unit 58 receives a security frame from the MAC frame processing unit 56 as a reception process. The security processing unit 58 confirms the contents of the security header in the security frame. When the message format is data with authentication, the decrypting unit 70 executes message verification processing. When the message format is encrypted data with authentication, the decrypting unit 70 executes message decryption processing and verification processing. If the message format is plain text, these processes are omitted.

  The encryption unit 68 generates a message authentication code (MAC) for the payload. Also, the payload and message authentication code (MAC) are encrypted. The decryption unit 70 verifies the message authentication code (MAC) targeted for the payload. Also, the payload and message authentication code (MAC) are decrypted. That is, the encryption unit 68 and the decryption unit 70 perform processing according to the message format, and have functions equivalent to those of the encryption unit 36 and the decryption unit 38 of the base station device 10. Therefore, the transmission process is the same as that of the encryption unit 36 of the base station apparatus 10, and the description thereof is omitted.

  The decoding unit 70 receives a security frame from the MAC frame processing unit 26 as a reception process. When the message format is data with authentication, the decrypting unit 70 verifies the message authentication code (MAC) added to the payload using the communication key. When the message format is encrypted data with authentication, the decrypting unit 70 decrypts the payload and the message authentication code (MAC) using the communication key, and verifies the decrypted message authentication code (MAC). Note that the decryption and verification are performed by a decryption algorithm corresponding to the encryption algorithm on the transmission side. When the message format is plain text, the decrypting unit 70 does not perform decryption and verification. Hereinafter, in this specification, it is assumed that verification of a message authentication code (MAC) or an electronic signature is also included in the broader decryption.

  Each configuration of the base station device 10 and the terminal device 14 can be realized in hardware by a CPU, memory, or other LSI of an arbitrary computer, and in software, it can be realized by a program loaded in the memory. However, here, functional blocks that are realized by their cooperation are depicted. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms only by hardware, or by a combination of hardware and software.

  FIGS. 8A and 8B are diagrams for explaining the data input timing to the decoding unit 70 and the decoding timing by the decoding unit 70. FIG. "Car 1", "Car 2", "Car 3", "Road 1/5", "Road 2/5", "Road 3/5", "Car 4", "Car 5", "Road 4 / “5”, “Road 5/5”, and “Car 6” each indicate a packet signal. “Car n” indicates a packet signal transmitted from the vehicle-mounted device, and “Road n” indicates a packet signal transmitted from the roadside device. “N / m” indicates divided data. FIGS. 8A and 8B show an example in which transmission data is encrypted on the roadside device side, divided into five divided data, and stored in five packet signals, respectively. 8A and 8B depict the arrangement of packet signals without being restricted by the definition of superframes and subframes for easy understanding.

  FIG. 8A shows data input timing and decoding timing according to the comparative example. The RF unit 52 and the modem unit 54 (hereinafter collectively referred to as a receiving unit) sequentially receive the packet signals. In FIGS. 8A to 8B, the receiving unit includes packet signals including undivided data (hereinafter referred to as single data) between a plurality of packet signals each including a plurality of divided data constituting or composing the entire data. Receive. More specifically, each of the “vehicles” including single data between the packet signal indicated by “Road 3/5” including the divided data and the packet signal indicated by “Road 4/5” including the divided data. 4 ”and“ Car 5 ”are received.

  The MAC frame processing unit 56 extracts data from the received packet signal. If the data included in the packet signal is not divided data, the MAC frame processing unit 56 outputs the extracted data to the decoding unit 70 without buffering. When the data included in the packet signal is divided data, the MAC frame processing unit 56 buffers the extracted data, and after all the divided data constituting the entire data are prepared, the divided data is sent to the decoding unit 70. Output.

  In the example illustrated in FIG. 8A, the MAC frame processing unit 56 immediately outputs the data extracted from the packet signals indicated by “car 1”, “car 2”, and “car 3” to the decoding unit 70. This is because these data are not divided data. The MAC frame processing unit 56 buffers the data extracted from the packet signals indicated by “path 1/5”, “path 2/5”, and “path 3/5”. This is because these data are divided data and not all the divided data are available. The MAC frame processing unit 56 immediately outputs the data extracted from the packet signals indicated by “car 4” and “car 5” to the decoding unit 70. Here, the order of reception and the order of input to the decoding unit 70 are switched.

  The MAC frame processing unit 56 buffers the data extracted from the packet signal indicated by “path 4/5”. When the MAC frame processing unit 56 extracts data from the packet signal indicated by “path 5/5”, all the divided data are collected, so “path 1/5”, “path 2/5”, “ The data indicated by “path 3/5”, “path 4/5”, and “path 5/5” are sequentially output to the decoding unit 70. The decoding unit 70 sequentially decodes data input from the MAC frame processing unit 56.

  FIG. 8B shows data input timing and decoding timing according to the embodiment. The receiving unit sequentially receives packet signals. The MAC frame processing unit 56 extracts data from the received packet signal. Regardless of whether the data included in the packet signal is divided data, the extracted data is output to the decoding unit 70 without buffering.

  In the example shown in FIG. 8B, the MAC frame processing unit 56 performs “car 1”, “car 2”, “car 3”, “road 1/5”, “road 2/5”, “road 3/5”. ”,“ Car 4 ”,“ Car 5 ”,“ Road 4/5 ”,“ Road 5/5 ”, and“ Car 6 ”, the data extracted from the packet signals are sequentially output to the decoding unit 70. FIG. 8B differs from FIG. 8A in that the received order matches the order input to the decoding unit 70.

  The decoding unit 70 sequentially decodes data input from the MAC frame processing unit 56. In the example shown in FIG. 8B, the decryption unit supports the encryption process before all the divided data constituting the entire data is prepared for the divided data included in the packet signal received by the receiving unit. The decoding process is sequentially executed for each packet signal. When the continuation of a plurality of divided data constituting the entire data is interrupted, the decoding unit 70 interrupts the decoding process of the divided data, and resumes the decoding process of the interrupted divided data when the continuation of the divided data is restored.

  In this embodiment, the message format of the data included in the packet signal received by the receiving unit is encrypted data with authentication. It is assumed that the data is encrypted by the AES-CCM mode. In the AES-CCM mode, a message authentication code (MAC) encrypted in the AES-CBC mode is generated. In the CBC mode, the result of encrypting the previous plaintext block is superimposed on the next plaintext by an exclusive OR operation, and the encryption process is executed on the result. The CBC mode is also called a chain mode because the previous encryption result is chained to the next block. The message authentication code (MAC) is generated by the representative value of each block obtained by dividing the data stored in the payload.

  Therefore, if the decoding unit 70 does not decode all the divided data constituting the entire data, the decoding unit 70 obtains the message authentication code (MAC) calculated from the representative value of each block and the added message authentication code (MAC). It cannot be compared and it cannot be determined whether the received data has been tampered with. When the decoding process for all the divided data is completed, it can be determined whether the received data has been tampered with. In the case of a configuration in which data is output to the reception processing unit 62 after it has been confirmed that the data has not been tampered with, the data output timing is also the time when the decoding processing of all the divided data constituting the entire data is completed.

  Comparing FIG. 8 (a) and FIG. 8 (b), the timing for completing the decoding processing of all the divided data is earlier in FIG. 8 (b), so the verification completion timing and data output timing are also shown in FIG. b) is faster.

  FIG. 9 shows a configuration of the decoding unit 70 according to the comparative example. The decoding unit 70 according to the comparative example includes a decoding processing unit 70a. Encrypted data is sequentially input from the MAC frame processing unit 56 to the decryption processing unit 70a. The order of the input encrypted data is as described with reference to FIG. That is, the plurality of divided data constituting the entire data are all input after being prepared.

  The decoding processing unit 70 a includes a decoding calculation unit 72, a work area 74, a determination unit 76 and an output buffer 78. The work area 74 includes a buffer or a register for temporarily storing information and parameters necessary for a decoding operation, such as a communication key, a CBC processing value, a nonce, and a count value, and intermediate data in the middle of the decoding operation. The decoding calculation unit 72 performs AES decoding calculation using the work area 74. The output buffer 78 temporarily holds data after decoding (hereinafter simply referred to as decoded data). The determination unit 76 verifies the decrypted data and determines whether or not tampering has occurred. When tampering is detected, the control unit 60 is notified. When determining that the decoded data is not falsified, the determination unit 76 outputs the decoded data held in the output buffer 78 to the reception processing unit 62.

  FIG. 10 illustrates a configuration 1 of the decoding unit 70 according to the embodiment. The decoding unit 70 according to Configuration 1 includes a selector 70b, a first decoding processing unit 70c, and a second decoding processing unit 70d. Encrypted data is sequentially input from the MAC frame processing unit 56 to the selector 70b. The order of the input encrypted data is as described with reference to FIG. That is, data is input in the order of reception regardless of whether it is divided data.

  The selector 70b outputs to the first decoding processing unit 70c when the input data is single data, and outputs it to the second decoding processing unit 70d when the input data is divided data. The first decryption processing unit 70c performs a decryption process on single data. The second decoding processing unit 70d performs a decoding process on the divided data. Therefore, when the reception unit receives a packet signal including single data, and when discontinuity occurs in a plurality of divided data constituting the entire data, the decoding process of the second decoding processing unit 70d is interrupted, and the second The decoding process of the 1 decoding processing unit 70c starts. When the reception unit receives the packet signal including the divided data and the continuity of the plurality of divided data constituting the entire data is restored, the decoding process of the second decoding processing unit 70d is resumed.

  The configuration of the first decoding processing unit 70c and the second decoding processing unit 70d is the same as the configuration of the decoding processing unit 70a. In the second decoding processing unit 70d, the decoded data of the plurality of divided data constituting the entire data is reintegrated by the output buffer 78. When there is a single output path from the decoding unit 70, a selector (not shown) is installed after the first decoding processing unit 70c and the second decoding processing unit 70d. The selector selects the decoded data from the first decoding processing unit 70 c and the reintegrated decoded data from the second decoding processing unit 70 d in the order of output, and outputs them to the reception processing unit 62.

  FIG. 11 illustrates a configuration 2 of the decoding unit 70 according to the embodiment. The decoding unit 70 according to Configuration 2 includes a decoding processing unit 70e. Encrypted data is sequentially input from the MAC frame processing unit 56 to the decryption processing unit 70e. The order of the input encrypted data is as described with reference to FIG. That is, data is input in the order of reception regardless of whether it is divided data.

  The decryption processing unit 70 e includes a decryption calculation unit 72, a work area 74, a determination unit 76, an output buffer 78, and a save area 80. That is, the save area 80 is added to the decryption processing unit 70a according to the comparative example. Hereinafter, differences from the decoding processing unit 70a according to the comparative example will be described.

  The save area 80 stores the result of the decoding process of the divided data. The evacuation area 80 is composed of an area for storing one piece of divided data and information and parameters necessary for a decoding operation related to the divided data. Further, instead of the divided data, it may be configured by one block data defined in the CBC mode and an area for storing the above-described information and parameters. The evacuation area 80 is operated by push pop. The push-pop timing is when new divided data is input. That is, in the save area 80, the last decoded data or block data and related information and parameters are always stored. Note that when the divided data constituting the new entire data is input, the decoding calculation unit 72 ignores the data, information, and parameters popped from the save area 80. The save area 80 is not used for the decryption process of the single data.

  The decoding calculation unit 72 stores the result of the decoding process of the divided data constituting the entire data in the save area 80, and executes the decoding process of the next divided data constituting the whole data from the save area 80 as described above. Get the result of. The result is the divided data or block data decoded by the decoding calculation unit 72 and related information and parameters.

  According to the embodiment of the present invention, when receiving a plurality of pieces of divided data divided after encryption, the decryption process for the divided data is sequentially performed in units of packet signals before the plurality of pieces of divided data constituting the entire data are gathered. By executing this, it is possible to suppress a delay in the end timing of the decoding process.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  8A to 8B show an example in which a plurality of packet signals including divided data are transmitted from one roadside device. In this regard, a plurality of packet signals including divided data may be transmitted from a plurality of roadside devices, respectively.

  In order to cope with this, in the configuration 1, a plurality of second decoding processing units 70d are provided. For example, eight are provided. The selector 70b associates the transmission source with one of the plurality of second decoding processing units 70d according to the transmission source ID (for example, the device ID of the roadside device). When the divided data is input, the selector 70b outputs the input divided data to the second decoding processing unit 70d corresponding to the transmission source ID.

  In configuration 2, a plurality of evacuation areas 80 are provided. Depending on the transmission source ID (for example, the device ID of the roadside machine), one of the transmission source and the plurality of evacuation areas 80 is associated. When the decoding operation unit 72 stores the result of the decoding process of the divided data in the save area 80 corresponding to the transmission source ID, and executes the decoding process of the next divided data received from the transmission source, The aforementioned result is acquired from the save area 80.

  In both configurations 1 and 2, the circuit scale increases as the number of pieces of data that can be decoded in parallel from a plurality of transmission sources is increased. Since the degree of increase in the circuit scale due to the increase in the number is larger in the configuration 1, the configuration 2 may be adopted when the number is designed to be large.

  In the above-described embodiment, an example in which the terminal device 14 receives a packet signal including divided data has been described, but the same processing can be applied when the base station device 10 receives a packet signal including divided data. . Further, in the above-described embodiment, an example in which the base station apparatus 10 transmits a packet signal including divided data has been described, but the same processing is applied when the terminal apparatus 14 transmits a packet signal including divided data. Is possible.

  10 base station device, 12 vehicle, 14 terminal device, 20 antenna, 22 RF unit, 24 modulation / demodulation unit, 26 MAC frame processing unit, 28 security processing unit, 30 control unit, 32 network communication unit, 34 data generation unit, 36 encryption Unit, 38 decoding unit, 50 antenna, 52 RF unit, 54 modem unit, 56 MAC frame processing unit, 58 security processing unit, 60 control unit, 62 reception processing unit, 64 notification unit, 66 data generation unit, 68 encryption unit, 70 decoding unit, 70a decoding processing unit, 70b selector, 70c first decoding processing unit, 70d second decoding processing unit, 70e decoding processing unit, 72 decoding operation unit, 74 work area, 76 determination unit, 78 output buffer, 80 save Area, 100 communication system 202 network, 212 area, outside 214 area.

Claims (2)

A packet signal divided data is included which divides the encrypted data, a reception unit that receives a packet signal including the individual data after encryption processing,
A decryption unit that executes a decryption process corresponding to an encryption process before all the divided data constituting the data before the division is prepared for the divided data included in the packet signal received by the reception unit; Prepared,
The receiving unit performs encryption while receiving a packet signal including one of a plurality of divided data obtained by dividing the encrypted data and a packet signal including another one of the plurality of divided data. Received a packet signal containing single data after processing
The decoding unit
A first processing unit that performs a decoding process on single data;
A second processing unit that executes a decoding process on the divided data;
A selection unit that supplies the received single data to the first processing unit and outputs the received divided data to the second processing unit;
A receiving apparatus comprising: This receiver is an in-vehicle device,
The receiving unit receives a packet signal including divided data transmitted from a roadside device during a road-vehicle transmission period, and receives a packet signal including single data transmitted from another vehicle-mounted device during a vehicle-vehicle transmission period. The receiving apparatus according to claim 1, wherein the receiving apparatus receives the signal.